Mercury and its salts have been discharged to water bodies, such as streams, rivers and lakes, from various sources, such as the liquid effluent from a sodium hydroxide- and chlorine-producing plant in which flowing mercury cathodes are used in the electrolysis of sodium chloride solutions.
This discharge has resulted in accumulation of mercury in various forms in river and lake bed sediments. Natural biological processes convert the mercury to a soluble organic form which is readily absorbed by fish and shell fish. Subsequent eating of the fish by animals, including man, results in accumulation of mercury in the animal body, which may lead to brain damage and ultimately death.
The mercury in the effluents often is at least partially in metallic form, as very minute droplets which are incapable of separation by normal physical separation techniques, such as centrifuging. The mercury also may be present in ionic or soluble organic form in the effluents. Various insoluble mercury salts also may be present in the effluent or the sediment accumulation.